Method and apparatus for transmitting ACK/NACK in TDD-based wireless communication system

Abstract

Provided are a method and apparatus for transmitting positive-acknowledgement (ACK)/negative-acknowledgement (NACK) in a time division duplex (TDD)-based wireless communication system. A user equipment receives an uplink grant which includes an uplink resource assignment and an uplink downlink assignment index (DAI), determines an ACK/NACK payload size on the basis of a value of the uplink DAI, and generates an ACK/NACK response for the at least one downlink transport block. The user equipment multiplexes the ACK/NACK response on an uplink transport block, and transmits the multiplexed ACK/NACK response.

The invention claimed is: 
     
       1. A method of transmitting positive-acknowledgement (ACK)/negative-acknowledgement (NACK) of a user equipment in a time division duplex (TDD)-based wireless communication system in which M downlink subframes (where M≧1) are associated with an uplink subframe, the method comprising:
 receiving from a base station an uplink grant which includes an uplink resource assignment and an uplink downlink assignment index (DAI); 
 receiving from the base station at least one downlink transport block in the M downlink subframes for each of a plurality of serving cells; 
 determining an ACK/NACK payload size on the basis of a value of the uplink DAI; 
 generating an ACK/NACK response for the at least one downlink transport block; 
 multiplexing the ACK/NACK response on an uplink transport block; and 
 transmitting to the base station the multiplexed ACK/NACK response by using the uplink resource assignment in the uplink subframe, 
 wherein the ACK/NACK response is generated for a specific number of downlink transport blocks, where the specific number is equal to at least the ACK/NACK payload size, 
 wherein the ACK/NACK response for the at least one downlink transport block is transmitted through a physical uplink shared channel (PUSCH) for transmitting at least one of uplink data and uplink control information, 
 wherein the ACK/NACK response for the at least one downlink transport block is generated by bundling the ACK/NACK for a plurality of downlink transport blocks in each of the downlink subframes only when uplink control information is transmitted through the PUSCH, 
 wherein the uplink DAI indicates a maximum value of the number of downlink subframes having at least one downlink transport block, 
 wherein the at least one downlink transport block is received on a physical downlink shared channel (PDSCH) having its corresponding physical downlink control channel (PDCCH) or on a PDSCH not having its corresponding PDCCH, and 
 wherein the at least one downlink transport block further includes a semi-persistent scheduling (SPS) release PDCCH indicating a release of semi-persistent scheduling. 
 
     
     
       2. The method of  claim 1 , wherein the downlink transport block includes at least one of data and control information requiring the ACK/NACK response. 
     
     
       3. The method of  claim 1 , wherein the ACK/NACK response for the at least one downlink transport block is generated by being bundled in a unit of serving cell. 
     
     
       4. The method of  claim 1 ,
 wherein the downlink transport blocks are received on respective PDSCHs, and the respective PDSCHs are indicated by a downlink resource assignment in a downlink grant on corresponding PDCCHs, and 
 wherein the downlink grant includes a DAI indicating an accumulative number of PDCCHs having assigned PDSCH transmission. 
 
     
     
       5. A user equipment for transmitting ACK/NACK in a TDD-based wireless communication system in which M downlink subframes (where M≧1) are associated with an uplink subframe, the user equipment comprising:
 a radio frequency (RF) unit for transmitting a radio signal; and 
 a processor coupled to the RF unit, wherein the processor is configured to:
 receive from a base station an uplink grant which includes an uplink resource assignment and an uplink DAI; 
 receive from the base station at least one downlink transport block in the M downlink subframes for a plurality of respective serving cells; 
 determine an ACK/NACK payload size on the basis of a value of the uplink DAI; 
 generate an ACK/NACK response for the at least one downlink transport block; 
 multiplex the ACK/NACK response on an uplink transport block; and 
 transmit to the base station the multiplexed ACK/NACK response by using the uplink resource assignment in the uplink subframe, 
 wherein the ACK/NACK response is generated for a specific number of downlink transport blocks, where the specific number is equal to at least the ACK/NACK payload size, 
 wherein the ACK/NACK response for the at least one downlink transport block is transmitted through a physical uplink shared channel (PUSCH) for transmitting at least one of uplink data and uplink control information, 
 
 wherein the ACK/NACK response for the at least one downlink transport block is generated by bundling the ACK/NACK for a plurality of downlink transport blocks in each of the downlink subframes only when uplink control information is transmitted through the PUSCH, 
 wherein the uplink DAI indicates a maximum value of the number of downlink subframes having at least one downlink transport block, 
 wherein the at least one downlink transport block is received on a physical downlink shared channel (PDSCH) having its corresponding physical downlink control channel (PDCCH) or on a PDSCH not having its corresponding PDCCH, and 
 wherein the at least one downlink transport block further includes a semi-persistent scheduling (SPS) release PDCCH indicating a release of semi-persistent scheduling.